The invention relates to a device for the electrochemical processing of a metal workpiece, comprising a plurality of electrodes that by way of respective linear drive units are movable in a linear manner relative to the workpiece from an initial position to a terminal position, said electrodes having a reproduction face that is directed toward the workpiece.
A method for electrochemical subtraction (ECM—electrochemical machining) is used for processing metal workpieces which are composed of an electrically conductive material when complex geometries are to be generated. A vane component of a turbomachine, for example a jet engine vane, or similar, is an example of a workpiece that can be produced by such ECM processing.
An ECM method is a reproduction method that does not involve chips. A device that serves this purpose comprises a plurality of electrodes which by means of a suitable linear drive unit are movable in a linear manner from an initial position, in the case of an as yet unprocessed workpiece, to a terminal position having a workpiece that then is processed. These movable electrodes form respective cathodes while the component forms the anode. A gap-type fluid duct which encircles the workpiece in a closed manner such that an electrolyte which absorbs and transports away the released material can circulate in said duct is formed during the entire reproduction method between the reproduction faces that are directed toward the workpiece and define the three-dimensional final geometry which the workpiece is intended to have, and the material surface per se.
Such a device is known, for example, from DE 10 2012 201 052 A1. The device therein that is conceived for the production of vanes of a turbomachine comprises a plurality of separate electrodes. When viewed in the longitudinal direction of the workpiece, therein thus the vane, and thus across the length of the vane blade between the vane root and the shroud ring, three electrodes which are movable relative to the vane surface at various angles are provided in the case of the device therein, this enabling the electrodes to move even below undercuts that are to be maintained. When viewed in the circumferential direction, thus around the vane blade per se, a total of six electrodes are provided, wherein the electrodes that configure the vane blade upper side and the vane blade lower side, when viewed in the longitudinal direction of the vane blade, are in turn composed of the three electrodes described. The electrodes that are disposed so as to be distributed around the circumference of the vane blade by way of respective linear drives are likewise moved in a linear manner in relation to the vane surface, said electrodes being mutually spaced apart during the movement and meeting one another only once the terminal position has been reached, so as to in this position configure the final three-dimensional blade geometry.
Since the electrodes, which are distributed around the circumference and between which respective sealing elements are provided in order for the fluid duct encircling the vane blade to be closed and sealed, are mutually spaced apart during almost the entire readjustment movement up to reaching the terminal position, or are converged only then, respectively, regions which are not processed or only inadequately processed consequently result between the individual electrodes, this resulting from the specific situation that no electrode or reproduction face, respectively, is assigned to or is opposite, respectively, said region between the mutually spaced apart electrodes. Respective material portions are therefore processed and removed only at the last moment, wherein this at times is even performed in that solid parts are removed, the bonding of the latter to the workpiece being severed only shortly prior to or upon reaching the terminal position by way of the electrodes which in this instance are very tightly converged.
A relatively inhomogeneous surface processing thus takes places, since no processing initially takes place in the regions between the adjacent and mutually spaced apart electrodes that are just being converged, said processing at times being only rudimentary even as the electrodes are progressively fed. Consequently, zones are invariably configured in the abutment region between two adjacent electrodes on the workpiece, the processing of said zones being different or inhomogeneous, respectively, in comparison to the processing of the adjacent faces that are engaged across by an electrode during the feeding movement of the latter. This leads to a surface of the finished workpiece that includes inhomogeneities.
Difficulties also result in particular in the region of the vane blade edges. The upper and the lower side of the vane blade are processed by way of large-area electrodes. Consequently, zones which are set at a very acute angle, up to a course that is parallel with the direction of movement of the adjacent electrode that processes the upper and the lower side thus arise in the region of the edges, thus where there are very tight radii. The difficulties described above result in particular in the edge region, where the operation in the prior art is carried out only by way of a very narrow electrode that processes the edge region, this electrode likewise converging with the adjacent upper-side or lower-side electrode only shortly prior to reaching the terminal position.